The purpose of this study is to investigate the identity and role of cytosol regulators of adenylate cyclase activity in rat reticulocyte membranes. We have previously shown in rat reticulocytes, that a cellular factor obtained from them markedly augments the ability of the beta-adrenergic catecholamines to stimulate adenylate cyclase activity. This factor appears to be different from guanine nucleotides and calmodulin, two established cytosol regulators of adenylate cyclase. We plan to continue our investigation of this regulator in studies designed to isolate and purify it. A second investigative approach we plan to take has as its ultimate aim delineation of the site(s) and mechanism(s) of action of the regulator protein.